1. Field of the Invention
The present invention relates to a working force quantity imparting member for imparting a working force quantity to an operation member, a working force quantity imparting structure using this working force quantity imparting member and a lens barrel to which an adequate working force quantity of an external operation ring is imparted.
2. Related Background Art
In this kind of lens barrel, there has hitherto been proposed a structure for reducing a sense of any play or shake by securing a working force quantity of an external operation ring. For example, Japanese Utility Model Publication No. 3-42409 discloses a structure in which a member elastically deformable in circumferential and radial directions is disposed between slide drums, thereby obtaining the working force quantity and a good touch of operation with less play or shake.
According to the prior art described above, however, it is, as a matter of fact, quite difficult to provide the member disposed between the slide drums with a proper elastic force and a good slidableness with a low frictional coefficient at a high level.
Particularly with respect to an durability, an abrasion between that member and the slide drum is easily caused. A method of supplying an oil may be considered for reducing this abrasion, however, there arises another problem in which to cause variations in terms of working load due to temperature changes and a permeation-leakage of the oil.